1. Technical Field
The present disclosure relates to a heat exchanger and an air conditioner.
2. Description of the Related Art
In WO 2016/194043 A, a heat exchanger is described, the heat exchanger including a plate-shaped fin having a first region where multiple cutout portions are formed at intervals in a longitudinal direction as a gravity direction and a second region where the multiple cutout portions are not formed in the longitudinal direction and flat pipes attached to the multiple cutout portions and crossing the fin. The fin is provided with protruding portions (hereinafter also referred to as “ribs”) protruding from a flat surface portion of the fin. Each first end portion of the protruding portions is positioned in the first region. Each second end portion of the protruding portions is positioned in the second region, and is positioned below the first end portion.
The protruding portion (the “rib”) is a reinforcement rib for preventing bending upon manufacturing of the fin by pressing.
A parallel flow heat exchanger is configured such that flat heat transfer pipes (hereinafter referred to as “flat pipes”) penetrate many fins stacked in parallel with each other. Performance of the heat exchanger is determined by, e.g., ventilation resistance when air passes through the heat exchanger or the efficiency of heat exchange between refrigerant flowing in the heat transfer pipe and air. In the case of comparison of a projected area as viewed in an air flow direction, the flat pipe has a smaller projected area than that of a circular pipe, and therefore, the ventilation resistance can be reduced. Thus, the flat pipe is sometimes employed for the purpose of reducing the ventilation resistance of the heat exchanger.
A configuration of a heat exchanger of a typical air conditioner will be described. The heat exchanger of the air conditioner mainly includes an evaporator configured to decrease a surrounding air temperature, and a condenser configured to increase the surrounding air temperature. When the surface temperatures of a fin and a heat transfer pipe of the heat exchanger used as the evaporator reach equal to or lower than a dew-point temperature of air, dew condensation occurs. Condensed water due to dew condensation drops along the fin due to gravity force, but is sometimes accumulated due to a narrow spacing between fins or adherence to a protruding object such as a cut-and-raised portion for defining a fin pitch. The condensed water accumulated between the fins closes an air flow path, and therefore, is a cause for a ventilation resistance increase.
When the fin surface temperature reaches below zero, freezing of the accumulated condensed water or frost formation on a fin surface occurs. The frozen condensed water or the frost is a cause for not only increasing ventilation resistance due to closing of the air flow path but also significantly lowering a heat exchange efficiency. Thus, the frost needs to be melted by regular defrosting operation. However, some or all of functions as the air conditioner are to be stopped, and therefore, performance of the entirety of the air conditioner is lowered. After the defrosting operation, the molten condensed water or frost adheres, as liquid droplets, to the fin surface. Thereafter, when the fin surface temperature reaches below zero again, newly-generated condensed water is frozen due to the liquid droplets or dew condensation caused by the defrosting operation.
Due to the above-described reasons, prompt drainage processing needs to be performed for water adhering to the fin and heat transfer pipe surfaces for maintaining performance of the heat exchanger.